1. Field of the Invention
The invention is directed to an arrangement for marking and measuring sections of track for the purpose of maintaining railroad tracks, particularly in the area of switches, crossovers, curves, and other sections of track that are susceptible to wear.
2. Description of Related Art
Measurements of track for determining maintenance areas are performed in a variety of ways in the art through optical, capacitive, and eddy current measurements. In this connection, automated measurement by measuring trains is usually not sufficiently precise for wear-critical areas to directly control exact work by work machinery (grinding machines or tamping machines). Therefore, there is a need for performing exact in situ measurement of work areas in track maintenance not only in a reliably reproducible manner but also so as to be closely linked to the work machine as far as possible. Computer-assisted measuring apparatuses in current use have so far not been reproducible with sufficient precision—particularly for complicated track areas such as curves or switches—with respect to the position of a work area when a work machine travels over the track area repeatedly and the work must always be resumed exactly at a determined location (determined beforehand by rail profile measuring equipment).
A measuring device which makes it possible to check the state of railroad track in track sections such as curved areas is described in DE 32 10 015 C2. This is a hand-held measuring device for measuring the lateral position and height position of railroad track which uses two reference chords, which are constructed as tripods which can be set up in a stationary manner at a defined distance from one another and have spirit levels, sighting optics and stadia rods, and has a stand base having a crosspiece for deploying on both rails. This measuring device measures the track position over long distances along a large chord of the curve arc and, in order to verify the measurement positions and the track position that is found in this way, further requires reference to fixed points (e.g., overhead line masts) which must be specified by the rail network operator. This does not allow track positions to be freely determined corresponding to the ascertained state of the track for maintenance of the track section.
Another measuring device for inspecting rails, particularly switches, is known from EP 1 548 400 A1. In this case, the rail spacing is detected by a laser distance sensor, an optical waveguide which projects the laser beam on the point to be measured, and a CCD receiver at the location to be measured.
Apart from the fact that the measuring device mentioned above uses optical sensors and, for this reason alone, is not suitable for use in work machinery such as grinding machines, EP 1 548 400 A1 discloses with regard to determining and recognizing the individual measuring points (which can lie at a distance of 2 to 5 mm) that these measuring points are recorded along the distances traveled, which are transmitted to a rotary encoder by the running wheels of the measuring device, and the measuring points are correlated with the measurements taken at the measuring points. This determination of measurement positions is not reproducible with exactitude due to slippage, particularly back-and-forth movements in the curve area, so that the correlation is unsatisfactory for controlling the locations where a work machine is put to use. Further, the rotary encoders present systematic errors which cause an accumulation of errors through wheel slippage during every forward and backward movement in the work area.
While visual detectability is desirable for non-contacting detection of positions, soiling caused by the work machinery impairs position detection of the measuring points so that visual methods cannot be employed in direct combination with work machinery (e.g., rail grinding machines). Consequently, a measuring device for finding measurement locations which have been determined beforehand by rail profile measuring equipment as defective sections of rail or which are defined by rules pertaining to measuring or machining must be designed in such a way that it is capable of reliably and reproducibly collecting position data along the track which cannot be falsified by ambient conditions.